I meant to enter this challenge at the beginning, but early spring, garden, yard work and indolence have gotten in the way, and will continue to do so. So I will not finish this anywhere near in time, but for me the challenge is really just to get it started. Also, hopefully others here will be able to point out where I am going wrong with this and give constructive criticism in the little time that is left.

I never met an "acoustic bass" I liked, so I'm going to try to build one. They all sound very thin in the lower register, and I'm guessing it's likely due to inadequate air volume in the soundbox. A guitarron has a much better low end, though its lowest note is only A 55Hz. I estimate its volume at somewhat less than 2 cubic feet. A 3/4 double bass sounds a lot better, but with a larger box of around 4 cubic feet (my guess.) I'm going to try to make one of about 2 cu ft, and hopefully light enough and of a configuration that it can be played hanging from my shoulders somewhat in the manner of a guitar, though with a more vertical orientation. I haven't decided yet if it will have frets or not. The body shape is an ellipse - a compromise between a rectangular box which maximises volume but is ugly, and a pinched waist which is lovely but loses volume. It gets larger toward the tail to try to add more air volume.

Here's a general plan of the shape and dimensions, though the width and depth will have to be slightly smaller as my wood is not quite wide enough. The construction techniques will generally follow that of a steel string guitar, though I've never built one - .

While jointing a board to use as a caul during one of these glue-ups, I failed to note a staple in the board. So as an added benefit to this challenge, I was able to learn how to sharpen and set up jointer blades.

Here's the top on the fretless acoustic bass that I made. It has a 17" lower bout and a 34" scale. Note that the bracing isn't nearly as beefy as what you propose. This bass works very well. I built it to accentuate the second harmonic since there's no way to get a strong fundamental on the low E string.

Getting the second harmonic strong involved two things: making the bridge/saddle combination tall enough that bridge rocked and torqued the top twice for every cycle of the string and making sure that the bridge was above the center of the lower bout so that when the bridge rocked the moving part above the bridge didn't cancel the moving part below. The bracing was done such that the top could move as much as possible but still support the string tension.